Sex is not just about penetration. Here are some ways the scenes could play out.
Doing stuff like her letting us finger her butt or giving her rimming until she climaxes seem to be like easy fits. Or, if we want to stick to sex being strictly penetration but still making it feel like it is between the two dickless individuals, maybe we could do it like Ryn where we use dildo and our hands.
Since doing it just by using a strap on instead of a dick just feels like a half hammered measure. While yes, you can technically do it that way, it is more of a byproduct of dick champs content and not something tailor made for vagina PCs. Same thing like with Kiyoko and her technically being able to be accessed to by female champs possessing that detachable shaft you get from Evergreen.
Another reason for why I am somewhat icky at that line of reasoning is because, at certain point, you can just go "Why are vagina only players complaining for lack of content compared to bedicked ones? They can use the magic strap, can't they?" for any time when there is a content drought for the girls/cboys. Technically yes, but those scenes are not the only reason people play as those types of PCs.
So yeah, anything that acknowledges that it is two dickless individuals doing it since it such a big deal for Cait and her romantic/sexual progression with the champ. Since she was saving her ass for someone important to her, to someone who she can trust. And for that important scene to be just sloppy seconds pussy only players recieve from bedicked ones just doesn't sit well with me.
I hope I made my reasoning clear.
Edit:You could also make it so that the scene acknowledges that you have a strap on since, if I remember right, game just treated it like a dick.